1. Field of the Invention
The invention relates generally to a method for removing by wipe or rolled film evaporation essential oils and antioxidants from extracts of organic material, more particularly organic material from the Lamiaceae (or Labiatae) family, including rosemary (Rosemarinus officinalis). The fraction containing antioxidants is suitable for addition to animal feeds and human food. The essential oils are pharmaceutical grade.
2. Background of the Prior Art
Worldwide demand for natural antioxidants has been rising due to safety concerns about synthetic food and feed additives and the public perception that natural food and feed supplements provide certain health benefits. The most important natural antioxidants being exploited commercially today are tocopherols. Tocopherols have a potent ability to inhibit lipid peroxidation in vivo by trapping peroxy-radicals (Burton, G. W., and K. U. Ingold (1989), in Vitamin E: Biochemistry and Health Implications, edited by A. T. Diplock, L. J. Machlin, L. Packer and W. A. Pryor, The New York Academy of Sciences, New York, pp. 7-22). Various herbal extracts for use as natural antioxidants are being explored. Possibilities include the extraction of rosemary or other botanical sources. Such new antioxidants may play a role in combating carcinogenesis as well as the aging process, and may be applicable in the nutraceutical industry.
Among the various natural extracts available in the market are rosemary extracts, which are reported to be highly effective in retarding lipid oxidation and protecting living cells from the damaging oxidative stress (Chen, Q., H. Shi and C-T Ho (1992), xe2x80x9cEffects of rosemary extracts and major constituents on lipid oxidation and soybean lipoxygenase activityxe2x80x9d, J Am Oil Chem Soc 69: 999-1002; Wong, J. W., K. Hashimoto and T. Shibamoto (1995), xe2x80x9cAntioxidant activities of rosemary and sage extracts and vitamin E in a model meat systemxe2x80x9d, J Agric Food Chem 43: 2707-2712). These extracts are described as being superior to vitamin E, a well-known natural antioxidant and food supplement, in many food model systems (Lolinge, J. (1983), Natural antioxidants in Allen, J. C. and R. J. Hamilton eds, Rancidity in Foods, Elsevier Applied Science, London, Chapter 6). However, opposite findings are also documented. Wong et al. (1995) revealed that vitamin E is more effective than rosemary extract in a cooked beef homogenate. Additionally, rosemary extract is shown to be a synergist of vitamin E in stabilizing or retarding oxidation in sardine oil and fish muscle (Fang, X. and S. Wanda (1993), xe2x80x9cEnhancing the antioxidant effect of xcex1-tocopherol with rosemary extract in inhibiting catalyzed oxidation caused by Fe2+ and hemoproteinxe2x80x9d, Food Res Int 26: 405-411; Wanda, S. and X. Fang (1992), xe2x80x9cThe synergistic antioxidant effect of rosemary extract and xcex1-tocopherol in sardine oil model system and frozen-crushed fish meatxe2x80x9d, J Food Process Preserv 16: 263-274).
As to the extraction of rosemary, many authors report that polar solvents yield extracts with higher antioxidant activities (Chang, S. S., B. Ostric-Matijasevic, C-L Huang and OA-L Hsieh (1977), xe2x80x9cNatural antioxidants from rosemary and sagexe2x80x9d, J Food Sci 42: 1102-1106). Chen et al. (1992) found that hexane extracts of rosemary contained a higher content of carnosic acid and carnosol than methanol extracts do. Carnosic acid and carnosol are the effective antioxidant molecules in rosemary. Carnosic acid and carnosol have been suggested to account for over 90% of the antioxidant activity of rosemary extracts (Aruoma, O. I, B. Halliwell, R. Aeschbach and J. Loligers (1992) xe2x80x9cAntioxidant and pro-oxidant properties of active rosemary constituents: carnosol and carnosic acidxe2x80x9d, Xenobiotica 22: 257-268). Antioxidant molecules in general, and rosemary antioxidants specifically, are by nature labile molecules especially when exposed to heat and/or air. During the harvest, the drying, and the regular solvent extraction of rosemary, some oxidation is likely to occur. Through a process of chemical reactions, carnosic acid, the naturally-occurring antioxidant molecule in rosemary, is believed to be the precursor to carnosol and many other antioxidants found therein (Wenkert, E., A. Fuchs, J. D. McChesney (1965), xe2x80x9cChemical artifacts from the family labiatexe2x80x9d, J. Org. Chem. 30: 2931-2934). It can be demonstrated that the freshly cut leaves of rosemary do not contain carnosol (Aeschbach, R. and L. Philippossian (1993), xe2x80x9cCarnosic acid obtention and usesxe2x80x9d, U.S. Pat. No. 5,256,700). Carnosic acid is about 10 times more effective as an antioxidant than carnosol (Aruoma et al., 1992), and it, therefore, is important for the high activity of a rosemary extract to minimize the damage to carnosic acid.
Essential oils are volatile oils which are the aroma and flavor components of organic material. They are used in a variety of products such as incense, aromatherapy oils, perfumes, cosmetics, pharmaceuticals, beverages, and foods. The market for these oils demands consistent high quality and reliable supplies at competitive prices. Essential oils are typically commercially extracted from organic material such as rosemary using steam distillation. In this prior art process, the antioxidants are destroyed, and thermal degeneration of the essential oils may occur.
An improved method for the simultaneous extraction of both antioxidant compounds and essential oils form species of the family Lamiaceae is described in pending patent application Ser. No. 09/206,458, which was filed Dec. 7, 1998, and is incorporated herein by this reference. Using tetrafluoroethane (TFE) in combination with one or more co-solvents, extracts of organic material are made that have a high level of antioxidant activity and further contain much of the essential oils present in the organic material. The essential oils are pro-oxidants, however, and further may limit the amount of the extract that may be used in certain antioxidant applications due to the odor of the essential oils. Further, essential oils of some species have a high market value apart from the antioxidant compounds. Accordingly, there is a need to remove and preserve the essential oils from the extract without substantially degrading the activity of the antioxidant compounds. There is also a need to purify further the antioxidant compounds, particularly carnosic acid, that may be present in the extract.
This invention is directed to a method of removing antioxidants and essential oils from the extract products of organic materials while preserving the activity of the compounds.
A purpose of the present invention is to provide a method using rolled film evaporation for removing antioxidants and essential oils from extracts of plants of the family Lamiaceae, particularly rosemary, that yields a fraction containing the essential oils of the plant material and a fraction that contains the antioxidant compounds present in the extract substantially free from odor and suitable for incorporation into animal feeds and human foods.
A further purpose of the present invention is to provide a method for removing antioxidants and essential oils from extracts of rosemary in high yields and high purity.
The organic material used during testing was dried, finely ground rosemary of the Arp variety. It is anticipated that the organic material can be any plant of the Lamiaceae family, and more broadly, any plant material which contains antioxidants and essential oils. It is also expected that any parts of the plant which contain the desired components may be extracted, as well as any form of the plant material (e.g., whole, ground, fresh, or dried).
Tetrafluoroethane (1,1,1,2) was used in the solvent blend. Tetrafluoroethane has a boiling point of xe2x88x9227xc2x0 C. The technology utilizes the vapor pressure of the solvent at room temperature and allows extraction under mild conditions, therefore minimizing the oxidative decomposition of carnosic acid during the extraction process. Tetrafluoroethane is substantially apolar and is preferably blended with acetone in the extractions of rosemary described here. The advantages of TFE show that it is non-flammable, has a low boiling point, is environmentally acceptable (very low toxicity), and is easily handled. Among numerous solvent blends tested, an 80/15/5 weight percent blend of TFE/methanol/acetone, respectively, proved to be an effective solvent resulting in a liquid extract with up to 130% of the efficacy of mixed tocopherols (when using plant material gathered from the publicly available rosemary variety Arp), and an antioxidant yield of about 60% of the rosemary antioxidants. The antioxidant efficacy of the liquid extract is lipid dependent. Oxygen bomb data presented in this disclosure was obtained using purified chicken fat. The antioxidant yield is based on a comparison of the total amount of antioxidants extracted from the same variety of rosemary using methanol as the sole solvent. Such methanol-only extracts, however, have undesirable physical characteristics.
The organic material and solvent blend are added together in a 1:3 (organic material:solvent blend) or higher (i.e., 1:4, 1:5, etc.) weight ratio to perform the extraction step in any vessel which will be compatible with the components. Since the TFE is preferably added in liquid form, the vessel has to be a pressure vessel which will withstand pressures equal to those required to maintain the TFE in liquid form. The extraction has been carried out at ambient temperatures, but the pressure and temperature may be varied, so long as the TFE and organic solvents remain in liquid form.
The method for removing the organic material from the solution was filtration. Any suitable separation process known to one skilled in the art which does not interfere with the other steps of the method may be used.
The removal of the solvent blend has been accomplished by evaporation. The TFE and organic solvent(s) may be removed by any suitable method known to one skilled in the art as well. A thin film evaporator has been found to be particularly suitable for this process.
The extract, after removal of the TFE, methanol and acetone, is passed through a rolled film evaporator under vacuum at a temperature in the range of about 65xc2x0 C. to about 120xc2x0 C., and preferably between about 80xc2x0 C. and 90xc2x0 C. The remaining volatile components of the extract include the essential oils of the organic material. These volatile compounds are evaporated in the rolled film evaporator and collected in distillate fractions. The residue is a viscous oily product that contains many of the antioxidant compounds that were present in the organic material. Because most of the essential oils were removed by the rolled film evaporator, the residue is essentially odor free and can therefore be used in applications where the extract containing the essential oils was found to be unsatisfactory, for example in protecting the fats in dog food from oxidation. The residue has a high percentage of antioxidant compounds. For example, the residue contains between about 10% and about 50% carnosic acid, and typically about 30% carnosic acid.
If the temperature of the rolled film evaporator is increased to between about 150xc2x0 C. and 195xc2x0 C., and preferably between about 160xc2x0 C. and 185xc2x0 C., the distillate is found to include the essential oils, as before, but it also exhibits antioxidant activity. It is believed that the antioxidant compounds present in the extract, for example, carnosic acid and/or carnosol, are evaporated at the higher temperatures and therefore are present in the distillate.
The essential oils resulting from rolled film evaporation at the lower temperature range are of very high purity (pharmaceutical grade) and surprisingly high yields (compared to previous extraction methods for obtaining essential oils). The distillate at the higher temperature range is a product which contains the essential oils but also exhibits antioxidant activity.